Although two races, differing in volatile leaf oils, were described by F. C. Vasek and R. W. Scora (1967) and confirmed by R. P. Adams et al. (1983), no differences were found in volatile wood oils (R. P. Adams 1987). To date, no morphological characters appear to be correlated with the chemical races. No other Western Hemisphere species of Juniperus has been found to have leaf-oil races.